Question

the active transport pump used in the membranes of gill cells in a freshwater fish has each of the following characteristics:
a it uses osmosis to carry sodium into the cells.
b it requires energy.
c it has a specific binding site for atp.
d it has a specific binding site for sodium ions.
e it is a protein.

Explanation:

Active transport is the movement of molecules or ions across a cell - membrane from a region of lower concentration to a region of higher concentration against the concentration gradient. It requires energy (usually in the form of ATP) and is carried out by membrane - bound proteins. These proteins have specific binding sites for the molecules or ions they transport and for ATP (which provides the energy). Osmosis is a passive process (diffusion of water across a semi - permeable membrane) and is not part of active transport.

Answer:

A. It uses osmosis to carry sodium ions into the cells. (This is incorrect as active transport is not osmosis)
B. It requires energy. (This is correct as active transport needs energy to move substances against the concentration gradient)
C. It has a specific binding site for ATP. (This is correct as ATP provides energy and binds to the transport protein)
D. It has a specific binding site for sodium ions. (This is correct as transport proteins have specific binding sites for the substances they transport)
E. It is a protein. (This is correct as active transport is carried out by membrane - bound proteins)